Malignant effusions from extranodal NK/T-cell lymphomas are frequently of anaplastic morphology with azurophilic granules and of T-cell lineage.

Our study revealed that ENKTL in the effusion might be characterized by anaplastic large cell morphology, cytoplasmic azurophilic granules, and a higher proportion of T-cell lineage as compared to de novo tumors arising from the prototypic sites. ENKTL rarely presented in effusion, which is associated with dismal outcome. Large international studies are warranted to validate these findings.